Additional dopamine reuptake inhibition attenuates vigilance impairment induced by serotonin reuptake inhibition in man

There is evidence for a specific impairment of human vigilance following enhancement of serotonergic activity by antidepressant drugs. In the present study, we investigated the putative role of serotonergic-dopaminergic interactions in diminished vigilance by comparing the attentional effects of sertraline, a selective serotonin reuptake inhibitor (SSRI) with additional mild dopamine stimulating effects, with those of paroxetine, a SSRI without dopamine activity, using a placebo-controlled, double-blind, three-way cross-over design. Twenty-one (of 24) healthy middle-aged subjects completed the three treatment periods of 2 weeks in which sertraline (50 mg, days 1-7; 100 mg, days 8-14), paroxetine (20 mg, days 1-7; 40 mg, days 8-14) and placebo were administered. Vigilance (Mackworth Clock Test), selective (Stroop, Dichotic Listening) and divided attention (Dichotic Listening) were assessed at baseline and on days 7 and 14 of each treatment period. Selective and divided attention were unaffected by SSRI treatment. Subchronic administration of paroxetine impaired vigilance performance at each investigated dose. Sertraline did not produce a significant decline in vigilance performance, presumably due to its concomitant effects on dopamine activity, counteracting the negative effects of serotonin on dopamine neurotransmission. It is concluded that a serotonergically mediated reduction of dopamine activity plays an important role in the reduction of human vigilance following SSRI administration.     

Influence of the selective serotonin re-uptake inhibitor,paroxetine, on gastric sensorimotor function in humans

BACKGROUND: The role of 5-hydroxytryptamine in the control of gastric fundus tone in humans is still unknown. Selective 5-hydroxytryptamine re-uptake inhibitors act both centrally and peripherally to enhance the availability of physiologically released 5-hydroxytryptamine. AIM: To study the influence of a selective 5-hydroxytryptamine re-uptake inhibitor, paroxetine, on gastric fundus tone, on the perception to gastric distension and on gastric accommodation to a meal. METHODS: Sixteen healthy volunteers underwent a gastric barostat study on two occasions, after pre-treatment with placebo or paroxetine, 20 mg/day. Graded isobaric and isovolumetric distensions were performed and perception was scored by a questionnaire. Subsequently, the amplitude of the gastric accommodation to a mixed liquid meal was also measured. RESULTS: Pre-treatment with paroxetine did not alter the thresholds for perception and discomfort during isobaric (4.7 +/- 2.3 vs. 4.0 +/- 2.0 mmHg and 13.3 +/- 3.1 vs. 12.7 +/- 2.3 mmHg above the minimum intragastric distending pressure, N.S.) and isovolumetric (307 +/- 90 vs. 417 +/- 114 mL and 772 +/- 74 vs. 750 +/- 76 mL, N.S.) distensions. Paroxetine significantly enhanced the amplitude of the meal-induced fundus relaxation (136 +/- 51 vs. 255 +/- 43 mL, P < 0.05). CONCLUSIONS: Pre-treatment with paroxetine enhances gastric accommodation to a meal. These data suggest that the release of 5-hydroxytryptamine, probably at the level of the enteric nervous system, is involved in the control of the accommodation reflex in humans, and that paroxetine may be beneficial to patients with impaired post-prandial fundus relaxation.     

Endocannabinoid control of gastric sensorimotor function in man

Aliment Pharmacol Ther 31 , 1123–1131

Summary

Background Little is known about the physiological role of the endocannabinoid system in the regulation of the motility and the sensitivity of the stomach. Endocannabinoid system dysfunction has been hypothesized to contribute to the control of food intake and the pathogenesis of functional dyspepsia. Aim To study the influence of rimonabant, the endocannabinoid 1 (CB1) receptor antagonist, on gastric sensorimotor function in healthy controls. Methods After 4 days of pre‐treatment with rimonabant 20 mg/day or placebo, 12 healthy volunteers (mean age 34 ± 12 years, six men) participated in a placebo‐controlled, double‐blind, randomized, crossover study with a gastric barostat assessment of gastric sensitivity to distension, gastric compliance, gastric accommodation and phasic motility on day 3 and a liquid nutrient challenge test on day 4. Results Rimonabant did not influence gastric compliance and sensitivity to distension. The meal‐induced gastric accommodation reflex was significantly inhibited by rimonabant (154.3 ± 30.9 vs. 64.3 ± 32.4 mL, P = 0.02). Rimonabant did not affect maximal nutrient tolerance or meal‐related symptoms during the satiety drinking test. Conclusion Endocannabinoids acting on the CB1 receptor are involved in the control of gastric accommodation in man.     

Clinical evidence for serotonin and norepinephrine reuptake inhibition of duloxetine

Most antidepressants in clinical use are believed to function by enhancing neurotransmission of serotonin [5-hydroxytryptamine (5-HT)] and/or norepinephrine (NE) via inhibition of neurotransmitter reuptake. Agents that affect reuptake of both 5-HT and NE (serotonin-norepinephrine reuptake inhibitors) have been postulated to offer greater efficacy for the treatment of major depressive disorder (MDD). These dual-acting agents also display a broader spectrum of action, including efficacy for MDD and associated painful physical symptoms, diabetic peripheral neuropathic pain, generalized anxiety disorder, and fibromyalgia syndrome. Substantial preclinical evidence shows that duloxetine, an approved drug for the treatment of MDD, generalized anxiety disorder, and the management of diabetic peripheral neuropathic pain, inhibits reuptake of both 5-HT and NE. This paper reviews clinical and neurochemical evidence of duloxetine's effects on 5-HT and NE reuptake inhibition. The clinical evidence supporting duloxetine's effects on NE reuptake inhibition includes indirect measures such as altered excretion of NE metabolites, cardiovascular effects, and treatment-emergent adverse event profiles similar to those for other drugs believed to act through the inhibition of NE reuptake. In summary, the data presented in this report provide clinical evidence of a mechanism for duloxetine involving both 5-HT and NE reuptake inhibition in humans and are consistent with preclinical evidence for 5-HT/NE reuptake inhibition.     

选择性5-羟色胺再摄取抑制药与性功能的关系

综述选择性 5 羟色胺再摄取抑制药 (SS RIs)与性功能的关系。SSRIs引起的性功能障碍中 ,最多见为射精延迟、性高潮缺乏或延迟 ,其次为性欲和唤醒困难。SSRIs与性功能的关系不应该认为是完全负面的 ,一些研究显示其有助于改善男性的早泄。SSRIs与性功能的关系可能与 5 羟色胺和多巴胺再摄取机制、催乳素高分泌、抗胆碱能作用、抑制氧化亚氮合成酶及累积倾向有关。已有多种措施用于克服SSRIs所致性功能障碍 ,西地那非可能是其中最为有效的药物治疗手段     

The serotonin reuptake inhibitor citalopram does not affect colonic sensitivity or compliance in rats

Altered serotonin signaling has been implicated in the pathophysiology of irritable bowel syndrome (IBS). Selective serotonin reuptake inhibitors (SSRI) improve IBS symptoms, although the mechanism of action remains unclear. We assessed the effects of the SSRI, citalopram, on colonic sensitivity and compliance in rats after acute and repeated administration. Colorectal distension was performed in conscious rats. Pressure–volume relationships during colorectal distension (2–20 mmHg), fitted using a power exponential model [Vol = V_max × exp[− (κ × RelP)^β], were used as a measure of colonic compliance. The visceral pain-related visceromotor response during colorectal distension (10–80 mmHg) was used to assess visceral sensitivity. Pressure–volume curves and visceromotor responses were assessed after acute citalopram (3 or 10 mg/kg, ip) or vehicle and after repeated treatment (7 and 14 days; 3 or 10 mg/kg/day). In vehicle-treated animals, pressure–volume curves were similar over time. Citalopram (acute or repeated treatment) did not affect neither the pressure–volume curves nor the visceromotor response to colorectal distension. Thus, citalopram, after acute or repeated administration, had no significant effects on colon compliance or visceral pain during colorectal distension in rats. These results agree with recent observations in humans suggesting that the therapeutic actions of citalopram in IBS are independent of any effects on colonic sensorimotor function.     

Treatment of depression in acute coronary syndromes with selective serotonin reuptake inhibitors

Depression in patients with acute coronary syndromes (ACS) is common and associated with impaired cardiovascular prognosis in terms of cardiac mortality and new cardiovascular events. It remains unclear whether antidepressant treatment may reverse these effects. In this review, the literature is evaluated on (i) the antidepressant efficacy of selective serotonin reuptake inhibitors (SSRIs) for depression in patients with ACS; (ii) the pleiomorphic effects of SSRIs that may be associated with cardiovascular prognosis; and (iii) the effects of SSRIs on cardiovascular prognosis.SSRIs provide modest relief of depressive symptoms in selected subgroups of depressed patients with ACS. With respect to the pleiomorphic effects of SSRIs, three mechanisms of how SSRIs may improve cardiovascular prognosis are discussed: via platelet function, via the autonomic nervous system (ANS) and via vasomotor tone. Some studies show that SSRIs may reduce platelet activity and sympathetic nervous system activation, but results are inconclusive. SSRIs are associated with vasodilation but this needs to be confirmed with in vivo experiments. Some non-experimental studies describe favourable effects of SSRIs on cardiovascular prognosis. Despite recent developments, much of the effect of SSRIs on cardiovascular prognosis remains unclear. Although some studies suggest effects of SSRIs on platelet function, ANS and vasomotor tone, which may lead to improved cardiovascular prognosis, results are largely inconclusive. More well designed studies addressing these questions are needed. Moreover, since the effects of SSRIs on depression itself are limited, efforts should be dedicated to study the diagnostic validity and homogeneity of depression in the context of ACS and the presence of clinically relevant subtypes.     

In vitro inhibition of pimozide N-dealkylation by selective serotonin reuptake inhibitors and azithromycin

Pimozide is often coprescribed with serotonin reuptake inhibitor (SSRI) antidepressants to treat depression in patients with Tourette's syndrome. In human liver microsomes (HLMs), the inhibition of the primary route of pimozide metabolism, N-dealkylation to 1,3-dihydro-1-(4-piperidinyl)-2H-benzimidazol-2-one (DHPBI), by four SSRIs (fluoxetine, sertraline, paroxetine, and fluvoxamine) and azithromycin was tested. Inhibition constants (K(i) values) were estimated from Dixon plots (three HLMs for each inhibitor) using the appropriate enzyme inhibition model by nonlinear regression. At 10 microM paroxetine, sertraline, fluoxetine, or fluvoxamine, the formation of DHPBI from pimozide (10 microM) in HLMs was inhibited by an average (three HLMs) of 7%, 7.7%, 8%, and 16%, respectively, whereas this inhibition did not exceed 55% at the maximum concentrations (100 microM) of the SSRIs tested. Azithromycin had negligible effect on pimozide (10 microM) N-dealkylation (19% at 100 microM azithromycin). These inhibition data were compared with ketoconazole, which was included as a positive control of CYP3A inhibition. At 0.1 microM and 0.5 microM ketoconazole, the formation of DHPBI from 10 microM pimozide was inhibited by 32% and 62%, respectively. The K(i) values (+/- SD) of ketoconazole, sertraline, fluvoxamine, azithromycin, fluoxetine, and paroxetine were 0.07 microM, 89 +/- 44 microM, 89 +/- 24 microM, 103 +/- 52 microM, 117 +/- 27 microM, and 129 +/- 33 microM, respectively. These values are least 100-fold higher than the expected plasma concentrations after the usual daily doses of the SSRIs and azithromycin, suggesting that coadministration of SSRIs and azithromycin are unlikely to markedly diminish the elimination of pimozide in patients. However, in vivo predictions from in vitro data are not always perfect. In vivo, the SSRIs or azithromycin may concentrate in the liver relative to plasma. In addition, the possibility that these drugs could alter pimozide disposition through effects on transport proteins or via promoter repression cannot be ruled out.     

PARP inhibition reduces acute colonic inflammation in rats

Poly(ADP-ribose) polymerases (PARP) comprise a family of enzymes which catalyse poly(ADP-ribosyl)ation of DNA-binding proteins. Multiple researches indicate the importance of PARP in promoting cell recruitment and thereby inducing organ injury in various forms of inflammation, such as colitis. We have evaluated the effects of two PARP inhibitors, nicotinamide and 1,5-dihydroxyisoquinoline, in acute colitis induced by trinitrobenzensulfonic acid (TNBS) in rats. Nicotinamide (20-40 mg/kg) and 1,5-dihydroxyisoquinoline (4-8 mg/kg) were administered 48, 24 and 1 h prior to the induction of colitis as well as 24 h later. 48 h after colitis induction the lesions were blindly scored and quantified as ulcer index. Histological study and colonic inflammation were assessed by gross appearance and myeloperoxidase (MPO) activity. Prostaglandin E2 (PGE2) synthesis and, cyclooxygenase-1 and cyclooxygenase-2 expressions by Western blotting and immunohistochemistry were also performed. Inflammation following TNBS induction was characterized by increased colonic wall thickness, oedema, diffuse inflammatory cells infiltration in the mucosa and necrosis. Furthermore, increased MPO activity, cyclooxygenase-2 expression and PGE2 synthesis were significantly augmented after TNBS instillation. On the contrary, treatment with 1,5-dihydroxyisoquinoline significantly reduced the degree of colon injury and also caused a substantial reduction in the rise in MPO activity, in the increase of staining for cyclooxygenase-2, as well as in the up-regulation of PGE2 caused by TNBS in the colon. Although nicotinamide significantly did not reduce macroscopic damage, it decreased both MPO activity and PGE2 colonic levels. In conclusion, we demonstrated that PARP inhibition can exert beneficial effects in experimental colitis and may, therefore, be useful in the treatment of ulcerative colitis.     

Differential effects of acute serotonin and dopamine depletion on prepulse inhibition and p50 suppression measures of sensorimotor and sensory gating in humans.

Schizophrenia is associated with impairments of sensorimotor and sensory gating as measured by prepulse inhibition (PPI) of the acoustic startle response and P50 suppression of the auditory event-related potential respectively. While serotonin and dopamine play an important role in the pathophysiology and treatment of schizophrenia, their role in modulating PPI and P50 suppression in humans is yet to be fully clarified. To further explore the role of serotonin and dopamine in PPI and P50 suppression, we examined the effects of acute tryptophan depletion (to decrease serotonin) and acute tyrosine/phenylalanine depletion (to decrease dopamine) on PPI and P50 suppression in healthy human participants. In addition, we also examined for the first time, the effects of simultaneous serotonin and dopamine depletion (ie combined monoamine depletion) on PPI and P50 suppression. The study was a double-blind, placebo-controlled cross-over design in which 16 healthy male participants completed the PPI and P50 paradigms under four acute treatment conditions: (a) balanced/placebo control, (b) acute tryptophan depletion, (c) acute tyrosine/phenylalanine depletion, and (d) acute tyrosine/phenylalanine/tryptophan depletion (combined monoamine depletion). Selective depletion of dopamine had no significant effect on either PPI or P50 suppression, whereas selective serotonin depletion significantly disrupted PPI, but not P50 suppression. Finally, the simultaneous depletion of both serotonin and dopamine resulted in significant reduction of both PPI and P50 suppression. We suggest these results can be explained by theories relating to optimal levels of monoaminergic neurotransmission and synergistic interactions between serotonergic and dopaminergic systems for normal 'gating' function. These findings suggest that a dysfunction in both serotonin and dopamine neurotransmission may, in part, be responsible for the gating deficits observed in schizophrenia, and their normalization following administration of atypical antipsychotic drugs.     

Serotonin, noradrenaline and cognitive function: a preliminary investigation of the acute pharmacodynamic effects of a serotonin versus a serotonin and noradrenaline reuptake inhibitor

Comparisons of the behavioural side-effect profiles of antidepressants that inhibit either serotonin or both serotonin and noradrenaline reuptake, may reveal differences in cognitive and psychomotor functions, which may be attributed to their relative pharmacological selectivity for potentiating monoamine neurotransmission in the central nervous system. The aim of the present study was to determine the acute pharmacodynamic effects of citalopram and venlafaxine, on cognitive and psychomotor performance. Nine healthy male volunteers received a single clinical dose of citalopram, venlafaxine or amitriptyline (positive control) in a double-blind placebo-controlled design. Cognitive and psychomotor tests and a subjective measure of sedation were examined before and 1, 2 and 4 hours after drug administration. Citalopram improved psychomotor responses to sensory stimuli and sustained attention, with significant decreases in movement times of the choice reaction time test and an increase in critical flicker fusion threshold. Venlafaxine did not affect performances on any of the cognitive or psychomotor tests examined. Differences may be related to relative potencies of the compounds for monoamine reuptake inhibition.     

Selective serotonin reuptake inhibitors in mixed anxiety-depression

The overlap between the depressive and anxiety disorders is extremely common. The introduction of the selective serotonin reuptake inhibitors (SSRIs) has, more than any other development, bridged the gap in terms of efficacy in both sets of disorders. A substantial body of data exists suggesting that the available SSRIs have substantial efficacy in anxiety symptoms co-occurring with depression. The clear utility of the SSRIs in disorders classified apart from depression is also established. Whilst panic disorder is the best studied, evidence on the efficacy of the SSRIs in disorders that previously did not attract much pharmacotherapeutic interest, such as social anxiety disorder and post-traumatic stress disorder is accumulating.     

Safety of selective serotonin reuptake inhibitors in pregnancy

Psychiatric treatment with selective serotonin reuptake inhibitors (SSRIs) may be desirable or necessary during pregnancy; however, the benefit of these treatments must balance the benefits to the mother with any risk to the developing foetus. At the present time, the role of serotonin in normal central nervous system development, as well as the effects of altering serotonin transmission at critical periods of embryo development, remains to be further clarified. Depression has a high prevalence in pregnant women (around 10%) and approximately one-half of the pregnancies are unplanned, making necessary that physicians have to know the risks associated with the decision to use this kind of antidepressants during pregnancy. The effects of antidepressants in pregnancy could be classified in several main categories: the teratogenic possible effects; the effects on the normal development of the brain and neuropsychological functions; the effects on birth weight and/or early delivery; the risk of increased bleeding on the mother during delivery; the neuropsychological behaviour and adaptation after delivery, including not only neonatal withdrawal syndromes but also pain reactivity and increased parasympathetic cardiac modulation during recovery after an acute noxious event and in a wide range of neurobehavioural outcomes; and medium- to long-term effects in neurocognitive functions in those children. These areas are reviewed according to the most recent published cohort-controlled studies and prospective surveys regarding SSRIs use in pregnancy. The review tries to clarify the blurred aspects of the use of SSRI during pregnancy and to give sensible and up-to-dated guidelines for the treatment of psychiatric disorders with SSRI during pregnancy.     

选择性5-羟色胺再摄取抑制剂对体重的影响

目的：探讨选择性5－羟色胺再摄取抑制剂（SSRI）对体重的影响。方法：复习近年的相关文献。结果：对临床上较少受重视的SSRI所致的重增加进行了讨论，内容包括体重增加的发生率、时程问题、增加幅度、可能的机制等。结论；SSRI引起的体重增加并不少见，应引起重视。     

Use of selective serotonin reuptake inhibitors and risk of developing first-time acute myocardial infarction

AIMS: Selective serotonin reuptake inhibitors (SSRIs) have been associated with serotonin depletion in platelets, potentially leading to abnormal aggregation and prolonged bleeding time. In view of the importance of serotonin in coronary thrombosis, and decreased platelet serotonin concentrations associated with SSRIs, the present study was performed to test the hypothesis of a decreased risk of acute myocardial infarction (AMI) associated with SSRIs. METHODS: We conducted a population-based case-control analysis using the UK General Practice Research Database (GPRD). A total of 3319 patients aged 75 years or younger free of clinical conditions predisposing to ischaemic heart disease, with a first-time diagnosis of AMI between 1992 and 1997, and 13 139 controls without AMI matched to cases for age, sex, general practice attended, and calendar time were included. Conditional logistic regression was used to estimate relative risks. RESULTS: Adjusted odds ratios (with 95% CI) for current use of SSRIs, non-SSRIs, or other antidepressants, compared to the group of nonusers of antidepressants were 0.9 (95% CI 0.5,1.8), 0.9 (95% CI 0.7,1.2), and 1.3 (95% CI 0.6,2.8), respectively. As compared with nonuse of SSRIs, current use (regardless of any other antidepressants used) resulted in an adjusted OR of 1.1 (95% CI 0.7,1.6). CONCLUSIONS: The current analysis provides evidence that SSRI exposure does not substantially decrease the risk of developing first-time AMI in patients free of factors predisposing to ischaemic heart disease. However, due to relatively small numbers of exposed subjects and the resulting wide confidence intervals, further studies may be needed to document a lack of effect of SSRIs in subjects without pre-existing diseases predisposing to AMI.